In an organization spread across many physical sites, it is common for users at each site to connect to a local electronic mail server, which can be regarded as a Post Office, to collect and receive electronic mail. Directory Synchronization is the process whereby multiple Post Offices or mail servers are able to automatically share their directories (lists of users and their mail ids).
FIG. 1 shows an electronic mail network having a plurality of post offices 10 each having a plurality of local users and a hub mail server H. The mail server H also acts as a directory synchronization server (DS Server), and in the case of an MS Mail network, there can be only one synchronization server on the network. Each post office maintains a directory of its local users and any changes in this directory, such as additions, deletions or amendments are sent to the DS Server at the hub. The DS Server in turn forwards these changes to each post office 10 so that any user connected to any post office can select any other user as a mail recipient. Mail from a user at one post office to a user at another post office is routed via the mail server to the destination post office where it is stored until the mail recipient checks its incoming mail with the destination post office.
In particular, in an MS Mail network, because only one DS Server is allowed, all MS Mail post offices must be designated as requesters for this DS Server. This makes the task of migrating to a new server extremely difficult as it means an all or nothing approach to migrating post offices to a new DS Server or manually synchronizing directories.